ADJUSTMENT BAR

Abstract: An adjustment bar (1) of effective variable length comprises a bar (4) which can be moved with respect to a housing (2). A piston (5) on the bar (4) divides the housing (2) into two chambers (6, 7) both of which are filled with a fluid (8). A fluid transfer link (9) interconnects the two chambers (6, 7) so that movement of the bar (4) within the housing (2) causes fluid to flow from one chamber into the other chamber. A locking means in the form of a tap (10) can be operated to prevent fluid flow through the fluid transfer link (9) thereby locking the bar (4) when it is as its required effective length.

Description: ADJUSTMENT BAR TECHNICAL FIELD This invention relates to an adjustment bar which has a variable length. BACKGROUND ART There are many types of adjustment bars available. One type of adjustment bar is a stabilising bar which is used on tractors and other agricultural vehicles to reduce or eliminate any undesirable sideways movement of agricultural implements attached to the vehicles. Stabilising bars generally comprise two rod members which are externally threaded with opposite pitch relative to each other. The rod members are mutually engagable into an internal threaded pipe. To provide extension or contraction of the stabilising bar, the pipe is rotated. To lock the length of the stabilising bar, nuts on the rod members are threaded until they contact the end of the pipe. Agricultural implements are usually attached to arms extending from the tractor. The stabilising bars are attached to the body of the tractor and to the tractor arms. The length of the stabilising bar is adjusted prior to the implement being attached or removed from the tractor arms. Unfortunately, adjusting the stabilising bars of the configuration described above is slow and labour intensive. Further, the bars are difficult to adjust in confined spaces. Other types of adjustment bars are known. Adjustment bars in the form of struts are used to control the rate that a door closes. These are essentially single acting hydraulic or pneumatic devices which can be locked to prevent movement in one direction only. Therefore, these devices will not be useful in situations where a adjustable variable length bar is required to prevent movement in more than one direction. A further disadvantage of the air or gas operated struts is that they cannot be used in aircraft. Another disadvantage with these adjustment bars is the means by which they are locked into position. This usually comprises a mechanical device in the form of a washer which is friction bearing and depends on pressure forcing the washer on the bar to provide the friction required. Thus, to set the washer one is required to hold the door open against the closing pressure, position the washer where required, then release the door and hope that the pressure on the washer from the bar will hold it in the desired position. Typically the washer slides some distance before it takes hold and it can be seen that this locking procedure is not a satisfactory one. Hydraulic rams are known in single acting and double acting forms. However, hydraulic rams have a number of disadvantages. One disadvantage is that usually there is required to be a separate hydraulic pumping system to activate the ram. This system is understandably bulky and expensive and inappropriate for use in situations where a variable length bar is required to be used as a stabiliser bar and the like. Other hydraulic variable length bars have reservoirs external to the bar into which fluid can flow. Again, these reservoirs are bulky and makes the bar unsuitable for use in certain situations. Another disadvantage of these bars is that the use of reservoirs makes the devices gravity dependent. Therefore, the devices can be used only in certain positions or orientations. It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided an apparatus for adjusting the position of a bar with respect to a housing, comprising housing having at least two chambers defined by the bar or an attachment or attachments thereto wherein movement of the bar is effected by fluid flow through a fluid transfer link from one chamber into another chamber. The housing may be divided into any number of chambers, but for ease of reference throughout this specification the housing shall be referred to as being divided into two chambers. A fluid in this specification is defined as any transferable flowable material such as a gas, liquid or particulate material. According to another aspect of the present invention there is provided apparatus for adjusting a bar substantially as described above wherein there is provided locking means for locking the bar into position by interrupting fluid flow between the chambers. It can be seen that this invention allows quick adjustment of the effective length a bar using fluid transfer between two chambers, wherein stopping the fluid flow locks the bar into position. In one embodiment of the present invention a cylinder is used for the housing of the adjustment bar and reference throughout this specification shall be made to the housing as being a cylinder. It must be appreciated however that any suitable housing may be used but preferably with a constant internal cross-sectional shape. The cylinder may be made of metal but any other suitable material may be used, such as polymers, ceramics, composites or other materials. Preferably the cylinder has a smooth internal surface which will be beneficial for sealing and to reduce friction and wear in the functioning of the device. For ease of reference the end faces of the cylinder shall now be referred to as heads. The heads of the cylinders may be held in the cylinder by screw threads, welded, friction fitted or by other means to locate the head to the cylinder. A suitable aperture can be provided for in each head through which the bar can pass. For optimum performance the bar is of constant cross-section except for the part which defines the chambers. This ensures that the absolute volume change in both chambers is constant when the bar is moved. The part or parts of the bar which divides the housing into the two chambers or the attachment to the bar which performs the same task shall now be referred to as a piston or pistons. In one embodiment of the present invention, each chamber can be filled with a fluid such as oil or water but it must be appreciated that any suitable fluid may fulfil this role. If the fluid is substantially non-compressible, preventing fluid flow between the chambers by a valve or tap will rigidly lock the bar into position. In another embodiment of the present invention the chamber can be filled with a compressible media such as air, combination of hydraulic fluid and air or any compressible gas, liquid or combination. This can then act as a shock absorption device as the bar will be allowed some movement to overcome shocks imposed during use from not being rigidly held into position. Each fluid chamber may have an aperture to which the fluid transfer link can be attached. The fluid transfer link can comprise a hose, tube, closed groove or any other suitable means. The fluid transfer link may be positioned in various configurations with respect to the housing. In some embodiments, the fluid transfer link is a tube which is positioned external to the housing. In one embodiment of the present invention the fluid transfer link is actually positioned within the bar itself and the only part of the fluid transfer link external to the housing is the part which attaches to the valve or tap. In alternate embodiments of the present invention the fluid transfer link may be internal to the adjustment bar. For example, there may be provided a central divider which is fixed to the inside of the cylinder, through which the bar passes. This central divider may include the fluid transfer link. The bar may have attached to it heads near the ends of the cylinder which help define the chambers within the cylinder. Movement of the bar causes the heads to likewise move pushing fluid through the fluid transfer link. A valve associated with the fluid transfer link can be used to control the flow fluid. Shutting the valve can stop the bar moving and lock it into position. The fluid transfer link may have a number of additional features and not be just a simple fluid conduit. For example, the fluid transfer link may have within it a floating piston in which there is a passage way through fluid can pass. This piston may be associated with shock absorbing means such as springs. Such an arrangement means that although the stabiliser bar can be set to an approximate length, some movement in the bar is allowed. This can be of use in situations whereby it is preferred that implements such as ploughs can float somewhat with respect to the vehicle that they are attached to. The amount of movement of the floating piston can be limited. For example, in addition to shock absorbing means (say springs) there may be provided an adjustable stroke limiter. This can come in a variety of forms and in one embodiment may be a pair of screws positioned on either side of the floating piston. The screws may be wound in and out to the appropriate distance to allow maximum movement of the floating piston. It should be appreciated that if these features are included in the main fluid transfer link, then the tap on the transfer link needs to have an adjustable orifice such as that found with needle valves. Otherwise, a separate fluid transfer link is required with the tap only capable of providing a fully open or closed orifice. In that embodiment the floating piston transfer link should have smaller apertures than that of the main fluid transfer link. In some embodiments, the apertures of the fluid transfer link will be near the cylinder heads so as to allow maximum travel of the bar within the cylinder housing. If there is a small gap between the apertures and the cylinder heads, then the fluid in this gap trapped between the piston on the bar and the cylinder head can act as a buffer preventing physical contact with the head and the piston as instead the fluid is compressed between the head and the piston. Appropriate sealing means (such as O-rings) may be used in the present invention to prevent leakage of the fluid. The fluid transfer link may have a fluid control means attached which is the locking means of the present invention. This fluid control means may be a tap, valve, or any other suitable control means. Throughout this specification the control means will be referred to as a tap. A tap can control the rate of fluid transfer from one chamber to the other by limiting the aperture through which the fluid can flow (such as with a needle valve). When the tap is in an open position the fluid can freely flow from one chamber to the other. When the tap is closed, the fluid flow is stopped and movement of the piston is halted and with an incompressible fluid the bar is locked into position. The tap can be controlled by a number means. In preferred embodiments, the tap is manually controlled by twisting same to expose or shut off an aperture which allows fluid to flow through same. In some embodiments, the tap can be remotely controlled for example by hydraulics or electronic means. Other methods of control are envisaged. In some embodiments of the present invention there may be provided with a means by which the bar can be automatically locked in a fully extended or withdrawn position. For example, the bar may have a central piston attached to it as described previously, but with the fluid transfer link within the piston itself. This fluid transfer link may have a valve associated with it which extends outside the piston. Thus, moving the bar and hence the piston to one end of the cylinder can cause the valve on the fluid transfer link to impact on the cylinder head. This can activate the valve and shut off the fluid transfer link thus automatically locking the bar into position. In other embodiments of the present invention there may be provided two fluid transfer links within the piston head where the valve extends on opposite sides of the piston for each transfer link. This enables the device to be held locked in a fully extended or withdrawn form. This feature could be particularly useful where the present invention is used to hold doors, windows and the like fully open or closed. In one embodiment of the present invention the adjustment bar may have a biasing means attached. The biasing means will be referred to as a spring but it must be appreciated that other means may be used such as elastic materials. The spring may be attached at one or both ends. An arrangement of the spring at either end may be used to return the bar to its original position when the fluid is free to flow. In some embodiments of the present invention, there may be provided in addition to the head at the end of the cylinder, a floating head within the fluid chamber. The floating head can act as a shock absorbing means. For example, the floating head may be fluid- tight so that incompressible liquid in the form of oil or water may be on one side of the floating head and a compressible fluid such as air on the other side of the head. Thus, when the bar is moved within the housing, there is some give or shock absorbing means provided as a consequence of the floating head pushing against the compressible fluid. Other shock absorbing means may be used. For example, there may be provided resilient rubber means which can absorb the impact of the piston against the cylinder head. In some embodiments there may be provided a shock absorbing means in the form of air filled pockets. The adjustment bar may be moved with respect to the housing by a variety of means. It is envisaged that when the adjustment bar is used as a stabilising bar for tractors, the bar will most likely to be moved by manual means. However, in other embodiments the adjustment bar may be moved by hydraulic, pneumatic or mechanical means. For example, mechanical means may come in the form of a screw or lever which applies pressure to the bar (or heads associated with it). It can be seen that by having a fluid transfer link between the two chambers of the cylinder, there is no need to have an external reservoir or hydraulic pumping means. Instead, the present invention offers a compact and inexpensive means by which the effective length of a bar can be varied. Further, the fact that a gravity dependent reservoir is not required means that the present invention can be used in any position or orientation. Using hydraulics means the present invention can be used in aircraft. Further locking means in the form of a fluid control means is a very simple way by which a bar can be locked into position and there is no need to rely on friction bearing locking means. And, unlike most mechanical locking means the present invention enables the bar to be adjusted to any length without the requirement of discrete steps such as in a ratchet system or pin and aperture systems. This invention may be used in many situations including as a stabilising bar for limiting lateral movement of tractor implements. This invention provides quick and easy adjustment so that implements may be attached or removed from the bottom link of. the tractor arms which hold the implement to be stabilised. Another possible use of the present invention is for holding gates, doors or windows and so forth open or closed. It should be appreciated that the configuration of the bar can swivel (or not as desired) and this feature can possibly be used in a variety of situations. Another possible use of the present invention is to use the adjustment bar as either a single acting displacement ram or a double acting ram. For example, the present invention may be configured so that it can be pressurised to either extend or withdraw the adjustment bar with respect to the housing. Once pressurised, the adjustment bar can be locked into position using a standard tap on the fluid transfer link enabling the pressurising means to be removed from the adjustment bar. This is particularly useful in situations whereby the bar is required to withstand great pressure, for example when used in preventing a drain in collapsing. BRIEF DESCRIPTION OF DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1: is a cross-sectional view of an adjustment bar in accordance with one embodiment of the present invention, and Figure 2: is a cross-sectional view of an alternative embodiment of the present invention, and Figure 3: is a cross-sectional view of an alternative embodiment of the present invention, and Figure 4: is a cross-sectional view of an alternative embodiment of the present invention, and Figure 5: is a cross-sectional view of an alternative embodiment of the present invention. BEST MODES FOR CARRYING OUT THE INVENTION Figure 1 illustrates a cross sectional view of an adjustment bar generally indicated by arrow 1. A cylinder 2 with a smooth internal bore forms the housing for the bar 1. Heads 3 are joined to the ends of the cy Under 2 and a circular aperture is centrally located in each head 3. A bar 4 of constant cylindrical cross sectional area passes through the entire length of the cylinder 2 and protrudes through the heads 3. The minimum length of the bar 4 is such that during movement of the bar 4 within the cylinder 2, any end of the bar 4 will not pass through the aperture in the heads 3. Located on the bar 4 is a piston 5 which forms a fluid-tight interface with the internal surface of the cylinder 2. The piston 5 creates two chambers 6 and 7 within the cylinder 2. Hydraulic fluid 8 fills both chambers 6 and 7. Near each head 3 are apertures 13 in the cylinder 2 to which a fluid transfer link in the form of a tube 9 is attached. This allows hydraulic fluid 8 to flow between chambers 6 and 7 when the bar 4 is moved. In operation, when the bar 4 is moved, the piston 5 forces hydraulic fluid 8 from one chamber to another. During this movement the change in volume of each chamber 6 and 7 is complementary. Therefore there is no net increase or decrease in the total volume and an external reservoir is not required. As a fixed attachment means 12 is fixed to the cylinder 2, motion of the bar 4 will increase or decrease the effective overall length of the adjustment bar 1. There is a slight gap between the apertures 13 and the heads. This gap prevents the piston 5 from impacting on the cylinder head 3 as it enables hydraulic fluid trapped in the gap to act as a buffer between the piston 5 and the cylinder head 3. The tube 9 has a locking means in the form of a tap 10 to adjust fluid flow between the chambers 6 and 7. As described, when the tap 10 is open, hydraulic fluid 8 can flow from chambers 6 and 7 to move the bar 4. To stop the movement of the bar 4, the tap 10 can be closed to prevent hydraulic fluid 8 from transferring from either chamber 6 or 7. With the tap 10 closed the incompressible fluid will lock the bar 4 into position and prevent movement in either direction. Seals 11 are located between the bar 4 and heads 3 and between the double acting piston 5 and the cylinder 2. The seals 11 prevent hydraulic fluid 8 from leaking to other sections. A compression spring (not shown) may be located at one or two ends of the cylinder. When the piston 5 is biased towards the spring, the spring is compressed. If the tap is then closed the bar 4 will be locked in position. When the tap is opened, the bar will be forced back to the uncompressed state of the spring. Compression springs may be located at either end so that the bar 4 may be biased to a central position. When the tap 10 is open the device may operate to adjust the bar 4 and then be returned to the central position. In a further example, the fluid 8 used is compressible. When the tap 10 is open the double acting piston 5 moves freely towards either head 3. When the tap 10 is closed the double acting piston 5 can be moved to balance the force on the bar 4. This will absorb any shock imposed on the bar 4 to prevent possible damage. Figure 2 illustrates an alternative embodiment of the present invention. In this embodiment there is a central partition 5a which is fixed with respect to the housing 2a. The bar 4a passes through this housing as does a fluid transfer link in the form of a passage 9a. Attached to either end of the bar 4a are pistons 14 and 15 which move with the bar 4a with respect to the housing 2a. The pistons 14 and 15 therefore act to define the chambers within the housing 2a. In this embodiment a valve in a the form of a tap 10a can close off the passage 9a within the central divider 5a, thus locking the bar 4a into position. Opening the valve 10a allows the bar and the pistons 14 and 15 to move within the housing 2a. Figure 3 illustrates yet another embodiment of the present invention. In this embodiment, the fluid transfer link 9b is internal to the bar 4b having apertures 13b on opposing sides of the piston 5b and the bar 4b. Internalising the fluid transfer link 9b provides a compact unit which can be used in a variety of situations. The only external part of the fluid transfer link 9b is where it attaches to the tap 10b which preferably is readily assessable. Figure 4 is an embodiment of the present invention which allows modest movement of the stabiliser bar 4c. In this embodiment, the fluid transfer link 9c has additional features. One of the additional features is a floating piston 16 which has a secondary fluid transfer link in the form of a passage 17 passing through it. On either side of the piston 16 are springs 18 which bear against the piston 16 and the internal surfaces of the fluid transfer link 9c. The springs 18 surround screws 19 which can be wound in or out to limit the maximum amount of movement permitted by the floating piston 16. The tap 10c has an adjustable orifice so that different amounts of fluid flow can pass through the fluid transfer link. In one embodiment, the tap 10c may be a needle valve. It can be appreciated that this embodiment of the present invention will be useful in stabilising bars used on tractor arms attached to ploughs which ideally should have a slight floating movement. Figure 5 illustrates an embodiment of the present invention which can be used as a double acting ram. In addition to the standard configuration illustrated in Figure 1 of this specification, the bar, generally indicated by numeral Id, has additional housing 20 in which a second movable piston 21 attached to the bar 4d is enclosed. The housing 20 has vent holes 22 and 23 positioned on either side of the piston 21. The housing 20 can be pressurised through the vent holes 22 and 23 until the ram is held into its desired position or length. The ram can be then locked into position by the tap lOd on the fluid transfer link 9d and the pressurising means removed from the vents 22 and 23. It can be seen that this embodiment of the present invention is particularly useful in situations whereby it is desired to hold apart ( or together) objects and matter. For example, this embodiment of the present invention could be used in preventing drains, mine tunnels and the like from collapsing. It should be appreciated that a single acting version of this embodiment having only one vent and piston may also have applications. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims: THE CLAIMS DEFINING THE INVENTION ARE: 1. An apparatus for adjusting the position of a bar with respect to a housing, comprising a housing having at least two chambers defined by the bar or an attachment or attachments thereto, wherein movement of the bar can be effected by fluid flow through a fluid transfer link from one chamber into another chamber. 2. An apparatus as claimed in claim 1 wherein there is provided a locking means for locking the bar into position by interrupting fluid flow between the chambers. 3. An apparatus as claimed in either claim 1 or claim 2 wherein the housing has a substantially constant internal cross-section. 4. An apparatus as claimed in claim 3 wherein the housing is in the form of a cy Under. 5. An apparatus as claimed in any one of claims 1 to 4 wherein the bar has a substantially constant cross-section. 6. An apparatus as claimed in any one of claims 1 to 5 wherein a piston attached to the bar defines the chambers within the housing. 7. An apparatus as claimed in any one of claims 1 to 6 wherein there is a locking means in the form of a tap which can operate on the fluid transfer link. 8. An apparatus as claimed in any one of claims 1 to 7 wherein there is provided a shock absorbing means. 9. An apparatus as claimed in any one of claims 1 to 8 wherein there is provided at least one floating head within the housing. 10. A stabihsing bar incorporating an apparatus as claimed in any one of claims 1 to 9. 11. A method of adjusting the effective length of a bar characterised by the step of using an apparatus as claimed in any one of claims 1 to 10. 12. An apparatus substantially as herein described with reference to and as illustrated by the accompanying drawings. 13. A stabilising bar substantially as herein described with reference to and as illustrated by the accompanying drawings. 14. A method substantially as herein described with reference to and as illustrated by the accompanying drawings.

Inventors: PEDERSEN GRAEME STANLEY, PEDERSEN, GRAEME, STANLEY
Applicants: PEDERSEN GRAEME STANLEY, PEDERSEN, GRAEME, STANLEY
Application year: 1994
Main classification: F15B15
IPC codes: E05C17, F15B15